Fatty acids hydrophobes from

The alkaline product from the wood ash was a crude solution of sodium and potassium carbonates called "lye". On boiling the vegetable oil with the lye, the soap (sodium and potassium salts of long chained fatty acids) separated from the lye due to the dispersive interactions between the of the fatty acid alkane chains and were thus, called "lyophobic". It follows that "lyophobic", from a physical chemical point of view, would be the same as "hydrophobic", and interactions between hydrophobic and lyophobic materials are dominantly dispersive. The other product of the soap making industry was glycerol which remained in the lye and was consequently, termed "lyophilic". Thus, glycerol mixes with water because of its many hydroxyl groups and is very polar and hence a "hydrophilic" or "lyophilic" substance. 

Step 2 - A patch pipet is removed from the solution, the polar head groups of the monolayer lipids are adsorbed to the interface while the fatty acid hydrophobic tails are exposed to the air ... 

In addition to the alkylated phenol mentioned, the hydrophobic part of the molecule may be derived from the fatty acids resulting from wax oxidation, and mercaptans from... 

The nature of the fatty acids in TAGs determines their hydrophobicity/hydrophih-city and diffusional mobility. In an aqueous/hpid environment, such as adipose tissue or lipoproteins in plasma, the relative hydrophihcity of the TAGs determines their partitioning between the interfacial phase and the apolar phase. This may have far stretching consequences. For instance, the rate and selectivity of fatty acid mobilization from fat cells may affect levels and composition of the nonester-ified fatty acids in plasma. These in mrn affect lipid homeostasis. Rate and selectivity of fatty acid mobilization from adipose stores are not related to the positional distribution of fatty acids on the glycerol backbone (75). They are related, however, to triacylglycerol hydrophihcity and thus to TAG structure (76). 

Figure 6-15. Synthesis of sphingolipids. NANA = W-acetylneuraminic acid G/c = glucose Gal = galactose GalNAc = N-acetylgalactosamine PIP = pyridoxal phosphate FA = fatty acyl groups derived from fatty acids = hydrophobic chains of ceramide. The dashed box contains the portion of ceramide derived from serine.

A potential substrate entryway (which presents anphipathic residues possibly to accommodate polar substrate head groups towards the FAAH active site) has been identified next to a-18 and a-19 helices, and it may indicate direct connection between the FAAH active site and the hydrophobic membrane bilayer. The mode for membrane binding of FAAH may facilitate movement of the FAA substrates directly from the bilayer to the active site, with no need for transport of these lipids through the aqueous cytosol. In this model, the substrate would first enter via the membrane to the active site following hydrolysis, the released fatty acid (hydrophobic) and amine (hydrophilic) products would then exit through the membrane-access and cytosolic-access channels, respectively. Moreover, the cytoplasmic port may serve the additional function of providing a way for a water molecule required for deacylation of the FAA-FAAH acyl-enzyme intermediate, which has been already characterized by LC-MS (Patricelli and Cravatt., 1999). 

Monovalent and polyvalent alkyl carboxylates are respectively called "soap" and "metallic soap." The straight chain of the fatty acids varies from C12 to C20. Higher members are too hydrophobic to be used and lower members have little surfactant value. Stearic acid soaps are doubtless the most widely utilized emulsifiers in oil-in-waier emulsions. Unsaturated fatty acid soaps such as oleate produce fluid emulsions (IS). The most common associated cations are sodium, calcium, magnesium, potassium, ammonium, and triethanolamine. Monovalent salts of carboxylic acids are generally used to produce oil-in-water emulsions. 

Each molecular region of capsaicin has been analyzed by means of systematic structural studies of the pungent and antinociceptive SARs. These studies revealed that capsaicin, dihydrocapsaicin, and V-vaniUyloctylamide (Fig. 3) are approximately equipotent, suggesting that either the overall size or the hydrophobicity (or both) are more important than the double bond and the branched side chain. Variation on fatty acid length, from C to Cn,... 

A Acylsarcosinates. Sodium A/-lautoylsarcosinate [7631-98-3] is a good soap-like surfactant. Table 4 gives trade names and properties. The amido group in the hydrophobe chain lessens the interaction with hardness ions. A/-Acylosarcosinates have been used in dentifrices (qv) where they ate claimed to inactivate enzymes that convert glucose to lactic acid in the mouth (57). They ate prepared from a fatty acid chloride and satcosine ... 

Ethoxylation of alkyl amine ethoxylates is an economical route to obtain the variety of properties required by numerous and sometimes smaH-volume industrial uses of cationic surfactants. Commercial amine ethoxylates shown in Tables 27 and 28 are derived from linear alkyl amines, ahphatic /-alkyl amines, and rosin (dehydroabietyl) amines. Despite the variety of chemical stmctures, the amine ethoxylates tend to have similar properties. In general, they are yellow or amber Hquids or yellowish low melting soHds. Specific gravity at room temperature ranges from 0.9 to 1.15, and they are soluble in acidic media. Higher ethoxylation promotes solubiUty in neutral and alkaline media. The lower ethoxylates form insoluble salts with fatty acids and other anionic surfactants. Salts of higher ethoxylates are soluble, however. Oil solubiUty decreases with increasing ethylene oxide content but many ethoxylates with a fairly even hydrophilic—hydrophobic balance show appreciable oil solubiUty and are used as solutes in the oil phase. 

Further addition of fatty acid eventually results in the formation of micelles. Micelles formed from an amphipathic lipid in water position the hydrophobic tails in the center of the lipid aggregation with the polar head groups facing outward. Amphipathic molecules that form micelles are characterized by a unique critical micelle concentration, or CMC. Below the CMC, individual lipid molecules predominate. Nearly all the lipid added above the CMC, however, spontaneously forms micelles. Micelles are the preferred form of aggregation in water for detergents and soaps. Some typical CMC values are listed in Figure 9.3. 

FIG. 1 Critical micelle concentration as a function of the number of carbon atoms in the hydrophobic rest of sodium a-sulfo fatty acid methyl esters. Methods O, surface tension +, conductivity A, solubilization of a dye x, solubility (all without electrolyte) , surface tension with a constant electrolyte concentration of 5 x 10"2 mol/L. (From Ref. 57.)... 

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